Cv boots are no problem really
As for the oil light, ideally you need to check the oil pressure, could be a blocked pick up pipe, could be a faulty pump, could even be a knackered engine
Even if the engine is knackered though you can pick up 2.0 bottom ends for not much money and standard bottom ends for peanuts
I think he is being a bit optimistic asking for £500, you seriously need to haggle that down after all it needs work for mot so obviously has ran out or is close to it and you have a potential buggered engine
What are you doing with the valver now then?